I've been using tiki-wiki for a while now. The templates are just so-so, but it does have a lot of features and permission levels. I heard it's basically a combination of joomla and a wiki. I've never tried any others though. What do you like about the ones you've tried?
Well, I've tried a bunch.. Joomla and Wordpress are among my favorites. Both work out-of-the-box and both have a very large "plugin" database.
Proper separation of design from the logic bits, friendly urls, usable interface, standards compliant output and modular in nature is always helpful. Wordpress is a great example of a proper web app. Joomla, meh, not so much. Nigel